1. Field of the Invention
The present invention relates to a new field sequential type color liquid crystal display device.
2. Description of the Related Art
In recent years, with an aim to save its energy, reduce its cost, and improve its resolution, there has been proposed a color liquid crystal display device that uses a field sequential method.
The color liquid crystal display principle based on the use of the field sequential method is the one wherein a liquid crystal display (hereinafter xe2x80x9cLCDxe2x80x9d) is used as a light shutter. By using a light source that is being lit, a light is sequentially radiated onto the LCD from the rear surface side of it while the lightness color of the light is being changed over with a high speed.
However, the above-described field sequential type color liquid crystal display device needs to be sequentially radiated, as described above, by means of the lighted-up light source from the rear surface of the LCD. It therefore had the problem that the power consumption resulting from the use of the light source is high, with the result that the device could not be applied to the liquid crystal display devices that had been constructed as battery-driven portable electronic appliances.
Also, the use of a reflection type liquid crystal display device using no light sources, i.e. having no power consumption resulting from the light source can be considered available.
Ordinarily, a color liquid crystal display element is of a micro color filter type having a construction of R (red), G (green), and B (blue). This micro color filter has a high light absorbance. Therefore, when an external light passes the micro color filter and is reflected by a reflection plate on the rear side of the liquid crystal cell and again passes through the micro color filter, the quantity of the light decreases down to ⅓ or less of the quantity of incident light. Further, from that value, the light has its half absorbed by the polarizing plate. Therefore, in the conventional reflection type liquid crystal display element, there is the problem that it is difficult to form a light image.
Especially, in the case of the reflection type liquid crystal display element, display of the white color is dark and therefore, for example, when letters are displayed as the black color, since the reflectance of the background white is low, the contrast is low. This posed the problem that the display is difficult to view.
The present invention has been made in view of the conventional points in problem and an object thereof is to provide a reflection type color liquid crystal display device whose power consumption is made small, and whose white display is made light, and a semi-transmission/semi-reflection type color liquid crystal display device whose light display on screen is possible, by using a new field sequential method.
The inventor of this application has been found out that a new field sequential system of reflection type color liquid crystal display device can be constructed by previously keeping the liquid crystal display element, for which a color filter having a construction of Y (Yellow), M (magenta), and C (cyan) is used, able to make the intended color display by controlling the picture elements of YMC in the way of simultaneously controlling these three picture elements and, on a time-sequential basis, controlling the respective transmittances thereof three times and, further, by, with the element being kept in that condition, incorporating a reflection sheet having per-color-reflection reflection regions on the rear surface side of that liquid crystal display element, namely on the backside of the LCD and moving it in synchronism with the changeover of the display of the color of the liquid crystal.
The object of the present invention is attained by a color liquid crystal display device comprising: a liquid crystal cell the pixel of which is constructed in the way of including three picture elements respectively having color filters of yellow, magenta, and cyan and in which in units of a pixel the light transmittances of these three picture elements are controlled, per frame of a screen to be displayed, simultaneously per three picture elements, and time-sequentially at least three times and which makes color display by the additive color process of that time-sequentially 3-time displayed colors; and a reflection device that is disposed at the position where the light passing through this liquid crystal cell goes in, where the reflection device includes a reflection sheet having three-color reflection regions arranged to reflect the color lights corresponding to the yellow, magenta, and cyan of the one frame and a driving device that drives this reflection sheet, sequentially in synchronism with the 3-time displays made by the picture elements in the liquid crystal cell, so as, with a combination of three time periods-a first time period in which the reflected light of yellow is combined with the transmittances of the three picture elements of yellow, magenta, and cyan in the liquid crystal cell; a second time period in which the reflected light of magenta is combined with the transmittances of the three picture elements of yellow, magenta, and cyan in the liquid crystal cell; and a third time period in which the reflected light of cyan is combined with the transmittances of the three picture elements of yellow, magenta, and cyan in the liquid crystal cell, to sequentially move that reflection sheet to the position of its selectively directing the incident light toward the liquid crystal cell.
Further, the present inventor has been found out that a field sequential system of semi-transmission/semi-reflection type color liquid crystal display device can be constructed by incorporating a semi-transmission/semi-reflection film having per-color transmission and reflection regions into the rear surface side of the LCD and further radiating light from the rear surface of that film and, in synchronism with the changeover of dark and light patterns corresponding to respective displayed colors of the LCD, moving that film.
The object of the present invention is attained by a semi-transmission/semi-reflection type color liquid crystal display device comprising a field sequential type of liquid crystal cell in which, per picture element, correspondingly to two or more pieces of colors in one frame of the screen to be displayed, the light transmittances are sequentially controlled and a semi-transmission/semi-reflection device that is disposed at the position where the external light passing through this liquid crystal cell goes in, where the semi-transmission/semi-reflection device includes a semi-transmission/semi-reflection film that includes two or more color regions colored to colors corresponding to the 1-frame displayed colors and the color regions of that have transmission and reflection regions, a light source that is disposed between the semi-transmission/semi-reflection film and the liquid crystal cell and that is disposed at the position of its radiating light to the liquid crystal cell from the rear surface of it, and a driving device that drives the semi-transmission/semi-reflection film so as, in synchronism with the timings with which to control the picture elements of the liquid crystal cell in the sequential order of colors, to sequentially move that film to the position of causing the two or more color regions to selectively transmit the outgoing light emitted from the light source in the direction directed toward the liquid crystal cell and causing those regions to reflect the incident light toward the liquid crystal cell.